Presently, there are no machines for household or curbside reprocessing of post-consumer plastic wastes. If there were any local recycling devices for plastic wastes, they would certainly find favour with eco-conscious : consumers, organizations and establishments, who might prefer to reprocess their own plastic wastes : Local reprocessing would enable individual wastes, such as polystyrene cups, PET bottles, PE bags, agricultural films, etc. to be reprocessed without getting contaminated by other wastes. This is important as repeated contamination of plastic wastes at several stages of collection and transportation is the main reason for the requirement of segregation and cleaning of plastic wastes.

It would obviously be better in environmental and economic terms to reprocess plastic wastes as close as possible to their source, if a method can be evolved to achieve this end at low cost, without causing pollution by the recycling process.

The invention gives a process and apparatus suitable for direct conversion of mixed thermoplastic wastes to its saleable constituents in forms of plastic pellets, moulded articles or fibres. The machines can be affordably installed at or near all places of origination of plastic wastes.

Household or curbside appliances based on the invention can work as "active litter-bins"to locally recycle lightly contaminated post-consumer plastic wastes.

DESCRIPTION OF THE PRIOR ART Plastic raw materials are traditionally traded in form of pellets. Plastic wastes are also recycled into pellets or lumps, before converting into useful articles. Pelletization of plastic wastes involves processes of cleaning, sorting, shredding, pulverizing, density separation, and extrusion into pellets of uniform shapes. Conventional reprocessing industry uses large and expensive machinery for each of these purposes.

Mixing of diftcrent plastics is bane of reprocessing of post-consumer plastic wastes. For avoiding this process, US Patent No. 5,263,841 has described a device for household production of plastic blocks out of homogenized plastic wastes. However, such blocks of impure plastics have little or nil commercial value.

Segregation of plastic components is essential to produce commercial grade of recycled plastic. Presently, one or more of the following methods perform segregation : l. Manual separation, 2. Separation of different plastics according to density variation. The medium for separation can be either air or water/liquid. Examples are cited in US Patent Nos. 05169005,4409098 3. Separation by using differences in solubility of plastics in different solvents. Examples are cited in US Patent Nos. 4946940,3553156 4. Separation based on differences in softening points and adhesive properties of different plastics at different temperatures. A process using this method is developed by Salyp N. V. and can be referred at http:/lwww. memagazine. org/backissues/april00/features/infrared/inf rared. html 5. Separation by using x-rays or spectroscopic analysis of plastic articles to determine their compositions, and initiate their separation.

Examples are cited in http://www.plasticrecycling.org/sort.htm

The above methods have following drawbacks : 1. Labour intensive, tedious and very costly method.

. Error-prone methods as incompatible plastics also have similar densities.

3. Expensive solvents get contaminated and partially consumed.

Disposal of process solvents adds to the pollution problem.

4. Expensive process. Cannot handle entanglements of wastes articles.

Exposed heating of plastics cause their degradation by exposure to atmospheric Oxygen and volatilization.

5. Extremely capital-expensive method.

OBJECTS OF THE INVENTION : The primary object of the present invention is to discover a simple and direct method for reprocessing mixed/unmixed post-consumer plastic wastes into usable pellets, moulded articles or fibres with use of simple technology and inexpensive machinery. This will enable reprocessing activity to be dispersed, rather than centralized. An immediate advantage of the technology would be to enable reprocessing of different types of plastic wastes by dedicated machines, located near the source of wastes or on curbsides. Many plastic wastes generated at. homes or offices, such as carry-bags, Styrofoam, PET bottles,, polystyrene beverage cups, etc. are quite pure at source, and would generate good recycled plastic if they are reprocessed without allowing their contamination.

However, it may be always not feasible to immediately reprocess different types of plastic wastes. With the best of intentions, other plastics can accidentally or inadvertently contaminate a"pure"batch.

The next important object of the invention therefore is to produce a method for automatic segregation of plastic wastes from each other, and non-plastic contaminants like paper, glass, metal.

Plastics have to re-process in closed chambers for preventing their oxidation and volatilization, and also to avoid atmospheric pollution. It is necessary to add beneficiating ingredients, such as plasticisers, resins, pigments, and filmers, to the plastic batch to improve the properties of the

intermediate or final output. Fillers such as sand can increase density of pellets allowing safe disposition of the heavy pellets in water bodies or landfills, without risk of their floatation. Other additives add value to the plastic by improving workability, colour, working life, or other attributes.

Thus the process and apparatus of the invention should anaerobically process plastics, and allow for mixing of additives.

DISCLOSURE OF INVENTION A typical embodiment of the invention is shown in the accompanying figures and described in the following description. The components of the embodiment are identified as: Figure 1 shows the section view of the preferred embodiment of the invention, which shows a low-cost vertical column cold-top extruder, designed for melting of typical household plastic wastes such as HDPE (milk) bags or PET (carbonated beverage) bottles.

Figure 2 to 4 show the post extrusion device options. The first option shown in figure 2 depicts a motorized scissors mechanism for cutting extruded plastic section into pellets that are immediately water-cooled and collected in a bin.

Figure 3 shows the second option in which molten plastic flows in an open compression mould placed below the machine. Simple solid articles like medallions, stoppers and nameplates can be moulded.

Figure 4 shows the third option of drawing the molten plastic in fibre form. Polymers like HDPE, PET are easy to draw as continuous fibres.

Good regulation of die temperature and extrusion pressure can produce reasonably good fibres that can be bunched, woven or knitted to produce useful plastic articles like ropes, woven belts, scrubbers, door mats, etc.

Figure 5 shows a scaled up embodiment of the invention designed for simultaneous segregated output of different plastic components from a mixed batch of plastic wastes. Non-melting contaminants are also continuously separated. This machine can work effectively as a curbside

'active litter-bin".

DESCRIPTION OF FIGURES Figure 1 shows the base stand 6 supporting tubular body 1 which holds the plastic wastes. Body 1 has hinge pin' 5 rotatably carry lid 26. Latch spring 24 latches lid 26 concentric to body 1 with latch 23. Lid 26 carries pressing motor 4 having internally threaded hollow rotor shaft 5. The motor turns shaft 5 to move lead screw 3 up'or down along with pressure plate 2. An internal keyway in lead screw 3 engages with an inward projecting stub of anti-rotation plate 27 to prevent rotation of screw 3 with shaft 5. In its lowest position, pressure plate 2 is approximately midway in body 1.

Electrical heater 8 banded around cylinder body 1 heats and melts plastic wastes 11 occupying the lowest level inside body 1. Pressure plate 2 never descends to this level, thus ensuring its freedom to slide within body 1 without getting jammed by resolidified molten plastic between its sides and body 1. flowing up its sides. The pressure plate connects to unmolten plastic wastes 9 in the top zone. Under this layer lies the middle zone of semi-molten plastics 10 at a temperature between deflection temperature and melting temperature of the major plastic components of the batch. The temperature of the lowest zone 3 is maintained equal to or slightly higher than the melting temperature of plastic that is to be extruded. This temperature can be progressively increased to extrude different plastic components progressively according to their melting/softening temperatures. The solid, semi-solid and liquefied plastic mass behaves as a non-Newtonian fluid, transferring pressure from the pressure plate downwards, with a continuous drop in pressure due to friction of side-walls. The molten plastic extrudes from the nozzle at bottom center of the body with this pressure and its own weight.. A metal sieve 7 resting on top of bottom plate 13 filters rion- molten plastic or non-plastic components from the plastic melt before reaching nozzle 38. A screw jack assembly installed on base stand 6 of body I lifts the bottom plate though insulation boards 14. Jack bolts 15 in a push plate press against base stand 6 to lift the insulation boards 14.

This seals the periphery of bottom plate 13 against the machined face in

the recess of pipe of body 1, preventing leakages. Extrusion die 12 is fitted to nozzle 38. Lower part of body 1, heater 8, and top portion of base stand 6 are all collectively insulated with ceramic wool insulation 16.

Figure 2 shows the motorized scissor mechanism in details. Pellet cutter motor 19 fixed on base stand 6 drives a double-faced cam 20. Each face of cam operates one of the scissor blades 21 that together cut the extruded strand into pellets 22. Bin 29 placed in water tub 41 under die 12 accumulates pellets and further cools them in water. Perforations in the bin allow flow of water to and from water tub 41, while automatically draining the water when removing the bin. Water-cooling of pellets 22 prevent them from adhering to each other and other metallic parts. The cutter motor 19 base suspends a water pump 28 inside the water tub. The water pump lifts water from the tub and pours it on the extruded plastic strand to form a solid crust and facilitate cutting. The warm water flows into the bin and back to the tub. Water tub 41 is rotated around column 33 for removing bin 29 out of the base 6 for removal of pellets.

Different plastic wastes such as polythene bags and PET beverage bottles soften and extrude from the die e at different temperatures between 130 deg. C and 190 deg. C respectively, as measured in the die. Unlike metals, plastics have no real"melting points". The stated melting points are indicate e of the temperatures at which the plastics lose almost all their viscosity and become free-flowing'out of small holes such as in die 12. The molten plastic cools by about 20 degrees while traversing the distance between heater 8 clamped around the lower part of body 1 and die 12. Due to this cooling, the plastic exits the die in semi-molten condition.

The RTD measures the temperature in centre of the die and the electronic temperature controller maintains it to the required set point. Polymer components like polyolefins have lowest melting points and are extruded at low temperatures. The differences in melting temperatures, or more correctly the melt-flow characteristics, help in separation of plastics by using the principle of fractional melting. With gradual increase in temperature of the melting zone, different plastic ingredients such as Polystyrene, Polypropylene, polyester, PET, etc get drained sequentially

from the same die.

Figure 3 shows a different option of a split mould'capable of directly hand-moulding recycled plastic in forms of small useful articles such as buttons, badges, name plates, etc. PET plastic waste can be moulded to make pre-forms suitable for stretch blow-moulding of the same articles as before.

For moulding purpose, plastic is extruded-at higher temperature than for forming pellets. Motorized gate plate 47 plugs the die till the mould is ready to receive the melt. On opening the gate, the mould gest filled with molten plastic that fills up the mould cavity to the desired level. The gate plate then plugs the die and the filled mould is closed, and allowed to cool. The moulded article is removed by opening the mould and the cycle is repeated.

Figure 4 shows another option to directly convert recycled plastic to fibres. The extruded plastic strand is guided through and cooled by a ring-cooling die 44. The strand is solidified before it reaches the bin where it turns around a fixed idler roller 46 to reach another idler mounted on dancing roller 42. The diameter of the strand and pulling speed is decided by many factors including the plastic composition, temperature of extrusion die, the pull on the fibre exerted by weight of the dancing roller, and the pattern of cooling. Steady conditions of temperature and cooling result in a fairly uniform size and output of fibre.

The fibre is wound around a motorized bobbin 45. The motor driving the bobbin wraps the fibre as it accumulates under the dancing roller, with the motor starting when the dancing roller reaches the bottom, and stopping when it reaches the top. This allows production of long lengths of plastic fibres that can be used for making various standed, knitted and woven articles such as cleaning mops, doormats, wire ropes, belts, multifilament ropes, etc.

Figure 5 shows another embodiment of the invention suitable for curbside operations. This machine is designed to handle heavily mixed plastic wastes. It is designed to continuously separate the components of the waste by using a process of fractional melting, in principle akin to the more commonly known process of fractional distillation. The main body of this machine Is placed horizontally and citizens deposit plastic wastes

in an overhead hopper at one end. A reciprocating electrically/ pneumatically/hydraulically operated actuator 30 is movable at one end of body. The pressure plate joined to the actuator normally presses plastic wates into the cyclinder body while pressing forward.

Intermittently, the pressing plate is retracted to admit plastic wastes from the hopper 36 into the cylinder body 1. The cylinder body has a series of nozzles at various points along the centerline, placed between heaters, optional air-blowers and RTD sensors, for maintaining the desired temperature profile across the length of the different zones. Plastic wastes are progressively heated as they pass each zone marked I to IV, and different components of plastic melt and extrude out of different dies <BR> <BR> fitted in the nozzles according to their order of melting. A second pneumatic/hydraulic/electromechanical actuator exerts controlled amount of backpressure on the counter-pressure plate 48 pressing against the open end of body 1. Non-melting residual wastes, including paper, plastic, stones, etc are discharged into the last collection chamber 40 D by lifting the plate 48. This discharge is suitable only for landfilling. The other collection chambers collect different plastics that extrude at different temperatures. Scissors mechanisms or other post-processing options as above are located under each die.

It is beneficial to have an increasing cross-section of cylinder body along direction of travel of the plastic mass to prevent clogging.

In a variation of the last embodiment of the invention, the body can be placed at an inclination to the horizontal layout described in figure 5; to derive benefits of gravity assisted forward flow of plastic.

BEST MODES FOR CARRYING OUT THE INVENTION For best results, it is always preferred to process a single type of plastic generated from a single process or product usage, in a recycling machine built according to the first embodiment of the invention. For example, a dedicated machine can be used in conjunction wth a coffee vending machine for recycling used coffee cups made from polystyrene. Special features can be provided to clean plastic wastes from known contaminants prior to recycling. In the above example of coffee cups, the likely impurities are beverage resides. Specific provision of rinsing and air drying of the plastic wastes before reprocessing would help to

improve the quality of output of dedicated machines.

The last described embodiment of the invention is very useful for kcrbsides, drop-boxes, offices, eating places, etc. where mixing of plastic wastes would be the rule. In such places, the machine has to continuously segregate the different plastic components to get reasonable throughput in fully automatic operations.

Other embodiments of the machines can have"reverse vending"features to reward the usage of the machine.

The simples embodiments of the invention can do without automation, and have the heater as the sole active electrical component. Pressure is applied by a ballast on top of the column of plastic wastes. The ballast is lifted by hand or foot to load fresh plastic into the machine. The extruded plastic is collected in form of lumps.

The embodiment described in figure I has an intermediate level of <BR> <BR> automation. It has a pressing motor, programmable temperature controller, pellet cutting device, water pump, exhaust fan and electrical interlocks. It also has a provision for removing non-melting contaminants from the melting chamber. Heater 8 of the embodiment is switched ON and OFF through the temperature controller operating around the set temperature. Low temperature plastics lilce LDPE melt at lowest temperatures, and extrude at temperatures as low as 120 deg. C measured near the die. High temperature plastics like PET/nylon melt at much higher temperatures and extrude from the same die only after the temperature is raised.

Anaerobic melting and internal scrubbing of gases is the special feature of the invention. The cold solid mass of plastic column in top zone of body I and lukewarm mass of deformed, compressed and semi-molten . plastic in the middle zone of body I act as sealant. These plastics recondense the volatile gases emitted from the molten plastic, and they also pevent atmospheric Oxygen from oxidizing the molten resins. A suction fan creates a negative pressure in the region of extrusion die, water tub and top of the body 1 to further ensure that the very small quantity of gas emissions are evacuated from a single point, allowing

appropriate gas treatment appliances like scrubbers can be installed to clean the eventual exhausts from any source of air pollution. Cooling of plastic extrusion within the long die, and immediate crust formation due to direct contact with water prevents oxidation and gas emissions from the extrusion.

In the preferred embodiment, non-melting impurities remain in the body as they do not melt at even the highest temperatures that the device can achieve. These are periodically removed by opening the bottom plate at the bottom of the body 1 with help of jack bolts 15. Without the bottom plate in place, body 1 is a through pipe and easy to clean with the heaters melting the plastic residues sticking to the inner sides of the cylinder body.

OTHER MODES FOR CARRYING OUT THE INVENTION Other embodiments of the invention can differ in construction from the preferred embodiment due to differences in capacity, application, cost and features beyond the essentials.

It is beneticial to"knead"plastic wastes in zones 1 and 2, for which one method would be to use two pressing plates each driven separately by its own screw mechanism. While feeding plastic wastes, both plates are retracted completely. However, while applying pressure, the two plates move alternately to cause kneading of the plastics in zones 1 and 2. This will help to extrude the lower temperature plastics, trapped within mass of higher temperature plastics, out of the die before the latter.

An embodiment of the invention has a screw feeder automatically dispenses specific additives to the plastic batch at one or more stages of passage through the machine from hopper to the extrusion die.

INDUSTRIAL APPLICABILITY The scope of the invention is not limited by the described embodiments, but includes all plastic melters/extruders in wllicll plastic wastes are intermittently admitted at one end of a closed cavity and pressed towards

other end by a pressure plate which always connects to unmolten plastic at the feeding end while molten plastic extrudes from the other end. A temperature gradient in the cavity causes plastic to heat and melt as it progressively travels in the cavity. Liquefied constituents of plastic drain through one or more extrusion dies, located in different temperature zones. Additional heaters are used to condition the plastic leaving the die for ease of its post-processing such as cutting into pellets or drawing into fibres. The invention allows fractional melting of plastics with or without the facility of melt-separation of its different constituents.

It would be obvious to one conversant with the art that there could be different constructions and forms of machines that could perform and benefit from the invention. One embodiment of the invention employs devices and instrumentation to measure and control the rate of plastic melt flowing out of the die. Another embodiment uses a combination of heating and cooling with air or water to control the zone temperatures to higher accuracy.

The extrusion dies can be heated and/or cooled in controlled manner to regulate or stop extrusion from any die. The overall scope of the invention is therefore limited only by the following claims.